Author Topic: Why are launches so sensitive to weather?  (Read 1535 times)

Offline Phronesis

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Why are launches so sensitive to weather?
« on: 01/18/2019 06:44 pm »
Hi all -- Why are rocket launches so sensitive to weather conditions, such that they're often canceled because of weather? Airplanes fly in all kinds of weather, and rockets are much more powerful. I'd expect rockets to be more resilient to weather than airplanes, but that doesn't appear to be the case...

Offline ejb749

Re: Why are launches so sensitive to weather?
« Reply #1 on: 01/18/2019 06:51 pm »
1) Lighting.  Rockets are full of explody stuff and sensitive electronics (see apollo 12 for what happens)
2) Upper levels winds have a much greater effect.
3) Freezing conditions can be bad (challenger)
4) Sometimes good launch video is required/desired.  Clouds can get in the way. 
(Especially during the late shuttle days when they needed to monitor dabris. )

Offline erioladastra

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Re: Why are launches so sensitive to weather?
« Reply #2 on: 01/19/2019 05:30 pm »
1) Lighting.  Rockets are full of explody stuff and sensitive electronics (see apollo 12 for what happens)
2) Upper levels winds have a much greater effect.
3) Freezing conditions can be bad (challenger)
4) Sometimes good launch video is required/desired.  Clouds can get in the way. 
(Especially during the late shuttle days when they needed to monitor dabris. )

Depending on the cargo - for example, humans -  you may also need to protect for an abort landing.

Offline MattMason

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Re: Why are launches so sensitive to weather?
« Reply #3 on: 01/19/2019 09:20 pm »
As learned from Apollo 12 (which had to launch through a rainstorm that day or, else, postpone the launch to another month because of launch windows), rockets can cause triggered lightning. It's the counterpart to static electricity you can generate on your own body that causes a shock when you touch something conductive.

As Apollo 12 illustrated, you didn't need a thunderstorm to make lightning--there were none around at that launch. Certain atmospheric conditions can increase the chances of triggered lightning that can zap the rocket or the pad.

Florida tanks more lightning than any other US state. About 35% of all launches from the Cape are postponed because of it. And it's why launch pads have those large lightning towers around them.

You might be interested on a document on the Lightning Launch Commit Criteria for both the Cape and VAFB.

https://ams.confex.com/ams/Annual2006/techprogram/paper_103803.htm


"Why is the logo on the side of a rocket so important?"
"So you can find the pieces." -Jim, the Steely Eyed

Offline Phronesis

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Offline hop

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Re: Why are launches so sensitive to weather?
« Reply #5 on: 01/21/2019 12:34 am »
Hi all -- Why are rocket launches so sensitive to weather conditions, such that they're often canceled because of weather? Airplanes fly in all kinds of weather, and rockets are much more powerful.
Aircraft also frequently adjust their flight plans to avoid severe weather. Unlike space launch vehicles, they have the flexibility to significantly vary their course while still flying the planned flight.
Quote
I'd expect rockets to be more resilient to weather than airplanes, but that doesn't appear to be the case...
Definitely not. Space launch vehicles tend to be built with lower safety factors, because the performance requirements are so much higher. Given the relatively low number and extremely high cost, occasional weather delays are an acceptable trade for performance.

Offline Jim

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Re: Why are launches so sensitive to weather?
« Reply #6 on: 01/21/2019 07:46 pm »
Hi all -- Why are rocket launches so sensitive to weather conditions, such that they're often canceled because of weather? Airplanes fly in all kinds of weather, and rockets are much more powerful. I'd expect rockets to be more resilient to weather than airplanes, but that doesn't appear to be the case...

Rockets are not more resilient than planes.

Offline John-H

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Re: Why are launches so sensitive to weather?
« Reply #7 on: 01/22/2019 01:37 am »
Large rockets lift off slowly and can be hard to control in the wind until they pick up speed.

On the other hand, they don't usually have to land.  :)

John

Offline Jim

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Re: Why are launches so sensitive to weather?
« Reply #8 on: 01/23/2019 07:19 pm »
Large rockets lift off slowly and can be hard to control in the wind until they pick up speed.

That doesn't apply to high altitude winds

Online Brovane

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Re: Why are launches so sensitive to weather?
« Reply #9 on: 01/23/2019 09:01 pm »
Are some rockets more sensitive to the weather than other rockets? 

"Look at that! If anybody ever said, "you'll be sitting in a spacecraft naked with a 134-pound backpack on your knees charging it", I'd have said "Aw, get serious". - John Young - Apollo-16

Offline Jim

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Re: Why are launches so sensitive to weather?
« Reply #10 on: 01/24/2019 02:49 am »
Are some rockets more sensitive to the weather than other rockets? 



See fineness ratio or tank thickness